716 Configuring L2 Multicast FeaturesMLD is a protocol used by IPv6 multicast routers to discover the presence ofmulticast listeners (nodes wishing to receive IPv6 multicast packets) on itsdirectly-attached links and to discover which multicast packets are of interestto neighboring nodes. MLD is derived from IGMP; MLD version 1 (MLDv1)is equivalent to IGMPv2, and MLD version 2 (MLDv2) is equivalent toIGMPv3. MLD is a subprotocol of Internet Control Message Protocol version6 (ICMPv6), and MLD messages are a subset of ICMPv6 messages.The switch can snoop on both MLDv1 and MLDv2 protocol packets andbridge IPv6 multicast data based on destination IPv6 multicast MACaddresses. The switch can be configured to perform MLD snooping andIGMP snooping simultaneously.What Is Multicast VLAN Registration?IGMP snooping helps limit multicast traffic when member ports are in thesame VLAN; however, when ports belong to different VLANs, a copy of themulticast stream is sent to each VLAN that has member ports in themulticast group. MVR eliminates the need to duplicate the multicast trafficwhen multicast group member ports belong to different VLANs.MVR uses a dedicated multicast VLAN to forward multicast traffic over theL2 network. Only one MVLAN can be configured per switch, and it is usedonly for certain multicast traffic, such as traffic from an IPTV application, toavoid duplication of multicast streams for clients in different VLANs. Clientscan dynamically join or leave the mutlicast VLAN without interfering withtheir membership in other VLANs.MVR, like IGMP Snooping, allows a layer 2 switch to listen to IGMPmessages to learn about multicast group membership.There are two types of MVR ports: source and receiver.• Source port is the port where multicast traffic is flowing to. It has to be themember of so called multicast VLAN.• Receiver port is the port where listening host is connected to the switch. Itcan be the member of any VLAN, except multicast VLAN.There are two configured learning modes of the MVR operation: dynamic andcompatible.• In the dynamic mode MVR learns existent multicast groups by parsing theIGMP queries from router on source ports and forwarding the IGMP joinsfrom the hosts to the router.
